FOAM MAT DRYING OF TOMATO JUICE

Experiments were carried out to determine the effect of drying air temperature and foaming agent (egg albumin) for production of tomato powder using foam-mat drying. Samples were prepared using tomato juice (4 degrees Brix total soluble solids), incorporating egg albumin as foaming agent (0, 5, 10, 15 and 20%, w/w). Foamed tomato juice (300 +/- 0.5 g) was spread on rectangular trays (2.5 mm thickness) and kept in tray dryer at 60, 65 and 70C air temperature. Incorporation of 10% egg albumin with 5 min of whipping time was found optimum for stable foam formation. The increase in foaming agent level enhanced the drying process (up to 15% egg albumin) and thereafter followed a decreasing trend. Foamed tomato juice can be dried in 510 and 450 min at 60 and 70C drying air temperature, respectively, with best acceptability. Effective moisture diffusivity of tomato juice ranged from 2.026 x 10(-8) to 3.039 x 10(-8) m(2)/s. PRACTICAL APPLICATIONS Tomato is the largest produced vegetable crop all over the world and 20-40% of produce goes as waste during postharvest operations per annum. Foam mat drying technology has been revamped and renewed attention for its added ability to process hard-to-dry materials to obtain products of desired properties and retain volatiles that otherwise would be lost during the drying of nonfoamed materials. In this context, the dehydrated tomato powder holds a promising and potential market for quality vegetable juices. Dehydrated powders can be reconstituted into juice and used as a starter for the preparation of products like sauce, ketchup, chutney, soups, baby foods, etc.